Betulinic acid (II) and betulinol (also known as betulin, III) are plant secondary metabolites of pentacyclic triterpenoids. The bark of silver birch has a high betulinol content which can reach 10 to 35%, and betulinic acid can be obtained from semi-synthesis of betulinol. Betulinic acid has biological activities of anti-malarial, anti-inflammatory and anti-HIV, and shows cytotoxic activity against a number of tumor cell lines, which is a promising precursor compound for application and development of anti-cancer and anti-AIDS drugs. Betulinic acid derivatives with excellent biological activities has been obtained by structural modifications to betulinic acid as a precursor compound. According to the structural characteristics of betulinic acid, it is mainly focused on the chemical modification sites at C-3, C-19 and C-28, and 30-halogenated betulinic acid (I) is an important intermediate for C-19 modification (N. V. Uzenkova et al., Bioorganic & Medicinal Chemistry Letters, 2005, 41:692; J. Y. Kim et al., Chemistry of Natural Compounds. 2001, 11:2405).

The synthesis of 30-brominated betulinic acid has been reported. In 1976, Achari et al. (Tetrahedron, 1976, 32(6): 741) published a paper entitled “Studies on Indian medicinal plants. XXXIX. Reinvestigation of the lactones and bromo derivative of betulinic acid”. In this method, 30-bromo betulinic acid is prepared by using betulinic acid as starting material, comprising protection of C-3 hydroxyl and C-28 carboxyl groups, subsequent C-30 bromination reaction and final deprotection. In 2008, a PCT patent entitled “Preparation of betulinic acid derivatives for use in antiviral and anticancer pharmaceutical compositions” was published (WO2008127364), which provides a method for preparing 30-bromo betulinic acid by using betulinic acid as starting material. Both the methods using betulinic acid as starting material are not suitable for large-scale production due to high production cost.